Liquid crystal display device

ABSTRACT

A liquid crystal display device of the present invention includes: a first substrate; a second substrate; a liquid crystal layer provided between the first substrate and the second substrate; and a plurality of picture element regions for displaying an image. Each of the plurality of picture element regions includes a transmission region in which an image is displayed in a transmission mode by using light that is coming from the side of the first substrate, and a reflection region in which an image is displayed in a reflection mode by using light that is coming from the side of the second substrate. The height of a surface of the second substrate on the side closer to the liquid crystal layer in the reflection region is greater than that in the transmission region, while the height of a surface of the first substrate on the side closer to the liquid crystal layer in the reflection region is substantially equal to that in the transmission region.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a liquid crystal display device,and more particularly to a transmission/reflection combination type LCDcapable of displaying an image in a transmission mode and in areflection mode.

[0003] 2. Description of the Background Art

[0004] In recent years, liquid crystal display devices, having desirablecharacteristics such as a small thickness and a small power consumption,have been widely used in various applications, including OA equipmentsuch as word processors and personal computers, PDAs (personal digitalassistance) such as electronic organizers, and camcorders with liquidcrystal monitors.

[0005] These liquid crystal display devices are generally classifiedinto those of reflection type and those of transmission type. A liquidcrystal display device is not self-luminous as is a CRT (cathode raytube) or an EL (electroluminescence) device. A transmission type liquidcrystal display device displays an image by using light from anilluminator (so-called “backlight”) arranged on the rear side of theliquid crystal display panel, and a reflection type liquid crystaldisplay device displays an image by using ambient light.

[0006] A transmission type liquid crystal display device, which displaysan image by using light from the backlight, is capable of producing abright display with a high contrast ratio without being substantiallyinfluenced by the brightness of the environment, but consumes a lot ofpower due to the backlight. Moreover, a transmission type liquid crystaldisplay device has a poor visibility under very bright environments(e.g., when used outdoor under a clear sky).

[0007] On the other hand, a reflection type liquid crystal displaydevice, which does not have a backlight, consumes little power, but thebrightness and the contrast ratio thereof are substantially influencedby the conditions under which it is used, e.g., the brightness of theenvironment. Particularly, the visibility lowers significantly underdark environments.

[0008] In order to overcome these problems, transmission/reflectioncombination type LCDs, which are capable of operating both in areflection mode and in a transmission mode, have been proposed in theart.

[0009] A transmission/reflection combination type LCD includes, in eachpicture element region, a reflection picture element electrode thatreflects ambient light and a transmission picture element electrode thattransmits light from the backlight, and is capable of displaying animage selectively in a transmission mode or in a reflection modedepending on the environment under which it is used (e.g., thebrightness of the environment). A transmission/reflection combinationtype LCD is also capable of displaying an image by using both modes atthe same time. Thus, a transmission/reflection combination type LCD hasa low power consumption, which is an advantage of a reflection typeliquid crystal display device, and is capable of producing a brightdisplay with a high contrast ratio without being substantiallyinfluenced by the brightness of the environment, which is an advantageof a transmission type liquid crystal display device. Moreover, thedecrease in visibility when used under very bright environments (e.g.,when used outdoor under a clear sky), which is a drawback of atransmission type liquid crystal display device, is suppressed.

[0010] As described above, a transmission/reflection combination typeLCD displays an image by using light from the backlight in atransmission region and by using ambient light in a reflection region.As a result, the number of times light passes through the liquid crystallayer in the transmission region differs from that in the reflectionregion. Therefore, the thickness of the liquid crystal layer in thetransmission region is set to be larger than that in the reflectionregion so that the optical path length for display light passing throughthe transmission region is matched with that for display light passingthrough the reflection region (see, for example, Japanese Laid-OpenPatent Publication No. 2000-305110). Typically, the thickness of theliquid crystal layer in the transmission region is set to be about twicethat in the reflection region.

[0011] However, for a liquid crystal display device in which thethickness of the liquid crystal layer in the reflection region is largerthan that in the transmission region, i.e., a liquid crystal displaydevice having a so-called “multi-gap structure”, the optimal structurefor forming multiple gaps has not yet been discovered. For example,Japanese Laid-Open Patent Publication No. 2000-305110 discloses a methodin which a step is provided on an active matrix substrate, which is oneof a pair of substrates opposing each other via a liquid crystal layertherebetween provided on the rear side of the device. The presentinventors have found that this structure has a problem of a decrease inthe brightness.

SUMMARY OF THE INVENTION

[0012] The present invention has been made in view of the above, and hasan object to provide a transmission/reflection combination type LCDhaving a multi-gap structure with a desirable display quality.

[0013] A liquid crystal display device of the present inventionincludes: a first substrate; a second substrate; a liquid crystal layerprovided between the first substrate and the second substrate; and aplurality of picture element regions for displaying an image, wherein:each of the plurality of picture element regions includes a transmissionregion in which an image is displayed in a transmission mode by usinglight that is coming from a side of the first substrate, and thereflection region in which an image is displayed in a reflection mode byusing light that is coming from a side of the second substrate; and aheight of a surface of the second substrate on a side closer to theliquid crystal layer in the reflection region is greater than that inthe transmission region, while a height of a surface of the firstsubstrate on a side closer to the liquid crystal layer in the reflectionregion is substantially equal to that in the transmission region. Thus,the object set forth above is achieved.

[0014] A thickness of the liquid crystal layer in the reflection regionmay be about ½ of that in the transmission region.

[0015] In one preferred embodiment: the second substrate includes acolor filter layer provided in the transmission region and in thereflection region; and a thickness of the color filter layer in at leasta portion of the reflection region is smaller than that in thetransmission region.

[0016] In one preferred embodiment, the second substrate includes atransparent substrate, and a first transparent dielectric layer formedbetween the transparent substrate and the color filter layer in theportion of the reflection region.

[0017] In one preferred embodiment: the color filter layer is providedon one side of the second substrate that is closer to the liquid crystallayer; and a second transparent dielectric layer is formed on the colorfilter layer in the reflection region.

[0018] In one preferred embodiment: the second substrate includes acolor filter layer provided in the transmission region and in thereflection region; and the color filter layer includes at least oneopening in a portion of the reflection region.

[0019] The at least one opening in the color filter layer may be aplurality of openings.

[0020] In one preferred embodiment: the color filter layer is providedon one side of the second substrate that is closer to the liquid crystallayer; and the second substrate includes a first transparent dielectriclayer formed in the at least one opening in the color filter layer, anda second transparent dielectric layer formed on the color filter layerand on the first transparent dielectric layer in the reflection region.

[0021] The first transparent dielectric layer and the second transparentdielectric layer may be formed integrally.

[0022] The first transparent dielectric layer and/or the secondtransparent dielectric layer may have a function of diffusing light.

[0023] In one preferred embodiment: the second substrate includes acolor filter layer provided in the transmission region and in thereflection region; and the color filter layer in the reflection regionis made of a material that is different from that of the color filterlayer in the transmission region.

[0024] In one preferred embodiment: the color filter layer is providedon one side of the second substrate that is closer to the liquid crystallayer; and a thickness of the color filter layer in the reflectionregion, which is made of a material different from that of the colorfilter layer in the transmission region, is larger than that of thecolor filter layer in the transmission region.

[0025] In one preferred embodiment, the color filter layer is providedon one side of the second substrate that is closer to the liquid crystallayer, and the second substrate includes a transparent dielectric layerformed on the color filter layer in the reflection region.

[0026] The color filter layer in the reflection region may have afunction of diffusing light.

[0027] In one preferred embodiment, the second substrate includes atransparent substrate, a color filter layer provided on one side of thetransparent substrate that is closer to the liquid crystal layer, and atransparent dielectric layer formed on the color filter layer in thereflection region.

[0028] The transparent dielectric layer may have a function of diffusinglight.

[0029] Another liquid crystal display device of the present inventionincludes: a first substrate; a second substrate; a liquid crystal layerprovided between the first substrate and the second substrate; and aplurality of picture element regions for displaying an image, wherein:each of the plurality of picture element regions includes a transmissionregion in which an image is displayed in a transmission mode by usinglight that is coming from a side of the first substrate, and thereflection region in which an image is displayed in a reflection mode byusing light that is coming from a side of the second substrate; a heightof a surface of the second substrate on a side closer to the liquidcrystal layer in the reflection region is greater than that in thetransmission region; and the second substrate includes a transparentsubstrate, a color filter layer provided on one side of the transparentsubstrate that is closer to the liquid crystal layer, a firsttransparent dielectric layer formed on the transparent substrate in atleast a portion of the reflection region and covered or surrounded bythe color filter layer, and a second transparent dielectric layerprovided in the reflection region so as to be located closer to theliquid crystal layer than the first transparent dielectric layer and thecolor filter layer. Thus, the object set forth above is achieved.

[0030] The first transparent dielectric layer may be formed between thetransparent substrate and the color filter layer and is covered by thecolor filter layer.

[0031] The color filter layer may include at least one opening in aportion of the reflection region, and the first transparent dielectriclayer may be formed in the at least one opening and is surrounded by thecolor filter layer.

[0032] The first transparent dielectric layer and the second transparentdielectric layer may be formed integrally.

[0033] A height of a surface of the first substrate on a side closer tothe liquid crystal layer in the reflection region may be substantiallyequal to that in the transmission region.

[0034] The present invention provides a transmission/reflectioncombination type LCD having a multi-gap structure with a desirabledisplay quality.

[0035] There is no unused region along the boundary between thetransmission region and the reflection region, and it is possible torealize a bright display, if a step is not provided on the surface ofone of a pair of substrates (first substrate) of the liquid crystaldisplay device that is provided on the rear side (the side opposite tothe viewer), but is provided only on the surface of the other substrate(second substrate) that is provided on the viewer side, so that theheight of the surface of the second substrate on the side closer to theliquid crystal layer in the reflection region is greater than that inthe transmission region, while the height of the surface of the firstsubstrate on the side closer to the liquid crystal layer in thereflection region is substantially equal to that in the transmissionregion.

[0036] Moreover, it is possible to precisely and easily control theoptical density of the color filter layer located in the reflectionregion and the thickness of the liquid crystal layer in the reflectionregion, if the second substrate includes a first transparent dielectriclayer for controlling the thickness, existence proportion, etc., of thecolor filter layer in the reflection region, and a second transparentdielectric layer for controlling the height of the surface of the secondsubstrate in the reflection region.

BRIEF DESCRIPTION OF THE DRAWINGS

[0037]FIG. 1A and FIG. 1B are plan views schematically illustrating aliquid crystal display device 100 according to Embodiment 1 of thepresent invention, wherein FIG. 1A is a plan view illustrating a TFTsubstrate 100 a, and FIG. 1B is a plan view illustrating the TFTsubstrate 100 a and a color filter substrate 100 b being attachedtogether.

[0038]FIG. 2 is a cross-sectional view schematically illustrating theliquid crystal display device 100 according to Embodiment 1 of thepresent invention taken along line 2A-2A′ in FIG. 1A and FIG. 1B.

[0039]FIG. 3A is a plan view schematically illustrating a conventionalliquid crystal display device 1000 in which a multi-gap structure isrealized by providing a step on the surface of an active matrixsubstrate 1000 a, and FIG. 3B is a cross-sectional view taken along line3B-3B′ in FIG. 3A.

[0040]FIG. 4 is a graph illustrating the relationship between thetransmission aperture ratio (%) and the unused region area ratio (%).

[0041]FIG. 5A and FIG. 5B are plan views schematically illustrating analternative liquid crystal display device 100′ according to Embodiment 1of the present invention, wherein FIG. 5A is a plan view illustratingthe TFT substrate 100 a, and FIG. 5B is a plan view illustrating the TFTsubstrate 100 a and the color filter substrate 100 b being attachedtogether.

[0042]FIG. 6 is a cross-sectional view schematically illustrating thealternative liquid crystal display device 100′ according to Embodiment 1of the present invention taken along line 6A-6A′ in FIG. 5A and FIG. 5B.

[0043]FIG. 7 is a cross-sectional view schematically illustrating aliquid crystal display device 200 according to Embodiment 2 of thepresent invention.

[0044]FIG. 8 is a cross-sectional view schematically illustrating aliquid crystal display device 300 according to Embodiment 3 of thepresent invention.

[0045]FIG. 9A and FIG. 9B are plan views schematically illustrating aliquid crystal display device 400 according to Embodiment 4 of thepresent invention, wherein FIG. 9A is a plan view illustrating the TFTsubstrate 100 a, and FIG. 9B is a plan view illustrating the TFTsubstrate 100 a and the color filter substrate 100 b being attachedtogether.

[0046]FIG. 10 is a cross-sectional view schematically illustrating theliquid crystal display device 400 according to Embodiment 4 of thepresent invention taken along line 10A-10A′ in FIG. 9A and FIG. 9B.

[0047]FIG. 11A to FIG. 11G are cross-sectional views schematicallyillustrating the steps of forming a color filter layer 42, a firsttransparent layer 44 a 1 and a second transparent layer 44 a 2 of theliquid crystal display device 400.

[0048]FIG. 12A and FIG. 12B are cross-sectional views schematicallyillustrating alternative steps of forming the first transparent layer 44a 1 and the second transparent layer 44 a 2 of the liquid crystaldisplay device 400.

[0049]FIG. 13A and FIG. 13B are plan views schematically illustrating aliquid crystal display device 500 according to Embodiment 5 of thepresent invention, wherein FIG. 13A is a plan view illustrating the TFTsubstrate 100 a, and FIG. 13B is a plan view illustrating the TFTsubstrate 100 a and the color filter substrate 100 b being attachedtogether.

[0050]FIG. 14 is a cross-sectional view schematically illustrating theliquid crystal display device 500 according to Embodiment 5 of thepresent invention taken along line 14A-14A′ in FIG. 13A and FIG. 13B.

[0051]FIG. 15 is a cross-sectional view schematically illustrating aliquid crystal display device 600A according to Embodiment 6 of thepresent invention.

[0052]FIG. 16 is a cross-sectional view schematically illustrating aliquid crystal display device 600B according to Embodiment 6 of thepresent invention.

[0053]FIG. 17 is a cross-sectional view schematically illustrating aliquid crystal display device 600C according to Embodiment 6 of thepresent invention.

[0054]FIG. 18 is a cross-sectional view schematically illustrating aliquid crystal display device 700 according to Embodiment 7 of thepresent invention.

[0055]FIG. 19 is a cross-sectional view schematically illustrating aliquid crystal display device 800 according to Embodiment 8 of thepresent invention.

[0056]FIG. 20A to FIG. 20D are cross-sectional views schematicallyillustrating the process of producing a color filter substrate 800 b ofthe liquid crystal display device 800.

[0057]FIG. 21 is a cross-sectional view schematically illustrating aliquid crystal display device 1100, which does not include a secondtransparent dielectric layer on a color filter layer.

[0058]FIG. 22 is a cross-sectional view schematically illustrating analternative liquid crystal display device 800′ according to Embodiment 8of the present invention.

[0059]FIG. 23 is a cross-sectional view schematically illustrating aliquid crystal display device 900 according to Embodiment 9 of thepresent invention.

[0060]FIG. 24 is a cross-sectional view schematically illustrating analternative liquid crystal display device 900′ according to Embodiment 9of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0061] The basic arrangement of a liquid crystal display device of thepresent invention will now be described.

[0062] A liquid crystal display device of the present invention includesa pair of substrates and a liquid crystal layer provided between thesubstrates, and has a plurality of picture element regions fordisplaying an image. In the present specification, a region of a liquidcrystal display device corresponding to a “picture element”, which isthe minimum unit of display, will be referred to as “picture elementregion”. In a color liquid crystal display device, R, G and B “pictureelements” correspond to one “pixel”. In an active matrix type liquidcrystal display device, a picture element region is defined by a pictureelement electrode and a counter electrode which opposes the pictureelement electrode. In a passive matrix type liquid crystal displaydevice, a picture element region is defined as a region where one ofcolumn electrodes which are arranged in a stripe pattern crosses one ofrow electrodes which are also arranged in a stripe pattern perpendicularto the column electrodes. In an arrangement with a black matrix,strictly speaking, a picture element region is a portion of each regionacross which a voltage is applied according to the intended displaystate which corresponds to an opening of the black matrix.

[0063] Each of the picture element regions of the liquid crystal displaydevice of the present invention has the transmission region in which animage is displayed in a transmission mode by using light coming from theside of one substrate (referred to as “first substrate”), and thereflection region in which an image is displayed in a reflection mode byusing light coming from the side of the other substrate (referred to as“second substrate”).

[0064] A transmission/reflection combination type LCD including thetransmission region and the reflection region in each picture elementregion preferably has a so-called “multi-gap structure”, in which thethickness of the liquid crystal layer in the reflection region is set tobe smaller than that in the transmission region so that the optical pathlength for display light passing through the transmission region ismatched with that for light passing through the reflection region.

[0065] However, the present inventors have found that if a multi-gapstructure is realized by providing a step on the substrate surface ofthe first substrate, which is provided on the rear side (the sideopposite to the viewer), there occurs a region along the boundarybetween the reflection region and the transmission region that does notcontribute to the display (unused region), thereby reducing thebrightness of the display. The reason why the unused region occurs willbe described later.

[0066] In contrast, there is no unused region along the boundary betweenthe transmission region and the reflection region, and it is possible torealize a bright display, if a step is provided only on the substratesurface of the second substrate, which is provided on the viewer side,so that the height of the surface of the second substrate on the sidecloser to the liquid crystal layer in the reflection region is greaterthan that in the transmission region, while the height of the surface ofthe first substrate on the side closer to the liquid crystal layer inthe reflection region is substantially equal to that in the transmissionregion.

[0067] This arrangement, which improves the display brightness in atransmission/reflection combination type LCD having a multi-gapstructure, will be referred to as “first arrangement”.

[0068] The second substrate provided on the viewer side typicallyincludes a transparent electrode and a color filter layer provided onthe transparent substrate. In a transmission/reflection combination typeLCD, the number of times light passes through the color filter layer inthe transmission region differs from that in the reflection region (oncein the transmission region and twice in the reflection region).Therefore, it is difficult to produce a bright display with a high colorpurity both in the transmission region and in the reflection region. Ifthe optical density of the color filter layer is set to be relativelyhigh so as to optimize the color purity in the transmission region,light passing through the reflection region is excessively absorbed bythe color filter layer, resulting in a dark display in the reflectionregion. On the other hand, if the optical density of the color filterlayer is set to be relatively low so as to increase the displaybrightness in the reflection region, the color purity in thetransmission region decreases.

[0069] If a transparent dielectric layer (referred to as “firsttransparent dielectric layer”) for selectively controlling the opticaldensity of the color filter layer in the reflection region is formed inthe reflection region, the decrease in transmittance in the reflectionregion can be suppressed while maintaining the optimal color purity inthe transmission region, whereby it is possible to produce a brightdisplay with a high color purity both in the transmission region and inthe reflection region.

[0070] The first transparent dielectric layer for controlling theoptical density of the color filter layer in the reflection region isformed so that the thickness, the existence proportion, etc., of thecolor filter layer in the reflection region are reduced from those inthe transmission region.

[0071] For example, if the first transparent dielectric layer isprovided between the transparent substrate and the color filter layer,the color filter layer is formed so as to cover the first transparentdielectric layer. Then, the thickness of the color filter layer locatedon the first transparent dielectric layer is reduced from that in otherregions due to a film thinning phenomenon that occurs when the colorfilter layer is formed. Therefore, even if the thickness of the colorfilter layer in the transmission region is set so that the color purityin the transmission region is optimized, it is still possible tosuppress the excessive absorption of light passing through thereflection region. Thus, it is possible to produce a bright display witha high color purity both in the transmission region and in thereflection region.

[0072] Alternatively, the color filter layer may include an opening in aportion of the reflection region, with the first transparent dielectriclayer being formed in the opening. With such an arrangement, a portionof light passing through the reflection region does not pass through thecolor filter layer but passes through the first transparent dielectriclayer surrounded by the color filter layer, whereby it is possible toimprove the transmittance in the reflection region. Thus, it is possibleto produce a bright display with a high color purity both in thetransmission region and in the reflection region.

[0073] In a case where the color filter layer is provided on one side ofthe second substrate that is closer to the liquid crystal layer, anothertransparent dielectric layer (referred to as “second transparentdielectric layer”) for controlling the height of the surface of thesecond substrate in the reflection region may be formed in thereflection region, in addition to the first transparent dielectriclayer. The second transparent dielectric layer is formed in thereflection region so as to be located closer to the liquid crystal layerthan the first transparent dielectric layer and the color filter layer.As a result, the height of the surface of the second substrate on theside closer to the liquid crystal layer in the reflection region isgreater than that in the transmission region. With such an arrangement,it is possible to control the height of the surface of the secondsubstrate in the reflection region, independently of the control of thethickness, the existence proportion, etc., of the color filter layer inthe reflection region. Therefore, it is possible to precisely and easilycontrol the optical density of the color filter layer located in thereflection region and the thickness of the liquid crystal layer.

[0074] This arrangement, which includes the first transparent dielectriclayer for controlling the optical density of the color filter layer inthe reflection region and the second transparent dielectric layer forcontrolling the height of the surface of the second substrate in thereflection region, will be referred to as “second arrangement”. Notethat the first transparent dielectric layer and the second transparentdielectric layer are typically non-colored layers.

[0075] By employing the “first arrangement” and/or the “secondarrangement”, it is possible to obtain a desirable display quality in atransmission/reflection combination type LCD having a multi-gapstructure.

[0076] Liquid crystal display devices according to the preferredembodiments of the present invention will now be described in detailwith reference to the drawings. Each of the liquid crystal displaydevices of the embodiments below employs at least one of the “firstarrangement” and the “second arrangement”. Note however that the presentinvention is not limited to the following embodiments.

[0077] Embodiment 1

[0078] The structure of one picture element region of a liquid crystaldisplay device 100 according to Embodiment 1 of the present inventionwill be described with reference to FIG. 1A, FIG. 1B and FIG. 2. FIG. 1Aand FIG. 1B are plan views schematically illustrating the liquid crystaldisplay device 100, and FIG. 2 is a cross-sectional view taken alongline 2A-2A′ in FIG. 1A and FIG. 1B. Note that FIG. 1A is a plan viewillustrating an active matrix substrate 100 a of the liquid crystaldisplay device 100, and FIG. 1B is a plan view illustrating the activematrix substrate 100 a and an opposing counter substrate 100 b beingattached together. Moreover, in subsequent figures, each element havingsubstantially the same function as the corresponding element in theliquid crystal display device 100 will be denoted by the same referencenumeral and will not be further described below.

[0079] The liquid crystal display device 100 includes the active matrixsubstrate (hereinafter referred to as “TFT substrate”) 100 a, thecounter substrate (hereinafter referred to as “color filter substrate”)100 b, and a liquid crystal layer 50 provided therebetween.

[0080] Moreover, the liquid crystal display device 100 includes thetransmission region T and the reflection region R for each of aplurality of picture element regions arranged in a matrix pattern, andis capable of displaying an image in a transmission mode and in areflection mode. An image can be displayed in either one of thetransmission mode and the reflection mode, or by using both displaymodes at the same time. The transmission region T is defined as a regionof the TFT substrate 100 a that has a function as an electrode forapplying a voltage across the liquid crystal layer 50 and also afunction of transmitting light therethrough. The reflection region R isdefined as a region of the TFT substrate 100 a that has a function as anelectrode for applying a voltage across the liquid crystal layer 50 andalso a function of reflecting light.

[0081] The TFT substrate 100 a includes a picture element electrode 20provided for each picture element region, a TFT (thin film transistor)30 as a switching element that is provided for each picture elementelectrode 20, a gate line (scanning line) 11 and a source line (signalline) 12 that are electrically connected to the TFT 30, a storagecapacitor line 13 running across the picture element region, etc. Thestructure will now be described in greater detail.

[0082] The TFT substrate 100 a includes a transparent insulativesubstrate 10 (e.g., a glass substrate), and further includes the gateline 11, a gate electrode 30G, the storage capacitor line 13, etc.,which are formed on the transparent insulative substrate 10. Moreover, agate insulating film 14 is formed so as to cover these elements. Asemiconductor layer 15, a channel protection layer (etching stopperlayer) 16, a source electrode 30S and a drain electrode 30D are formedon a portion of the gate insulating film 14 that is located above thegate electrode 30G. These elements together form the TFT 30. The gateelectrode 30G of the TFT 30 is electrically connected to the gate line11, the source electrode 30S to the source line 12, and the drainelectrode 30D to a connection electrode 17. The gate line 11 and thesource line 12 are each made of a metal such as tantalum. In the presentembodiment, the storage capacitor line 13 is formed from the same filmin the same step as the gate line 11.

[0083] An interlayer insulating film 18 is formed so as to coversubstantially the entire surface of the transparent insulative substrate10, on which the TFTs 30 have been formed. A transparent electrode 22 isformed on the surface of the interlayer insulating film 18, and areflection electrode 24 is formed on the transparent electrode 22. Thetransparent electrode 22 is made of a transparent conductive materialsuch as ITO, for example, and the reflection electrode 24 is made of ahigh-reflectance metal such as aluminum or silver, for example. Thetransparent electrode 22 is electrically connected to the connectionelectrode 17 via a contact hole 18 a formed in the interlayer insulatingfilm 18, and is electrically connected to the drain electrode 30D viathe connection electrode 17. The reflection electrode 24 is electricallyconnected to the drain electrode 30D via the transparent electrode 22.The transparent electrode 22 and the reflection electrode 24, which areelectrically connected to the drain electrode 30D, together function asthe picture element electrode 20. In the present embodiment, the pictureelement electrode 20 partially overlaps with the gate line 11 and thesource line 12 via the interlayer insulating film 18. Moreover, thestorage capacitor line 13 is electrically connected to a counterelectrode 46 provided on the color filter substrate 100 b, and forms astorage capacitor together with the connection electrode 17 and the gateinsulating film 14.

[0084] In the liquid crystal display device 100, the reflectionelectrode 24 defines the reflection region R, and a portion of thetransparent electrode 22 on which the reflection electrode 24 is notformed defines the transmission region T.

[0085] The reflection electrode 24 defining the reflection region R ismade up of a reflection electrode 24 a that overlaps with the storagecapacitor line 13, a reflection electrode 24 b that overlaps with thegate line 11, and a reflection electrode 24 c that overlaps with thesource line 12. The storage capacitor line 13 has a width of 35 μm inthe direction in which the source line 12 extends (the direction Y inFIG. 1A and FIG. 1B), and the reflection electrode 24 a overlapping withthe storage capacitor line 13 also has a width of 35 μm. Moreover, thereflection electrode 24 b overlapping with the gate line 11 has a widthof 4 μm in the direction in which the source line 12 extends, and thereflection electrode 24 c overlapping with the source line 12 has awidth of 41 m in the direction in which the gate line 11 extends (thedirection X in FIG. 1A and FIG. 1B). Note that the thickness of thereflection electrode 24 is preferably equal to or greater than 0.1 μmand less than or equal to 0.15 μm. When the thickness of the reflectionelectrode 24 is less than 0.1 μm, the reflection characteristicsdeteriorate, whereby light coming from the side of the counter substrate100 b may possibly be transmitted therethrough. On the other hand, whenthe thickness of the reflection electrode 24 is greater than 0.15 μm,the difference between the height of the transparent electrode 22 andthat of the reflection electrode 24 may affect the control of theoptical path length in the reflection region R and that in thetransmission region T. Forming the reflection electrode 24 with athickness greater than 0.15 μm may be industrially wasteful becausesufficient reflection characteristics can be obtained if the thicknessof the reflection electrode 24 is as large as about 0.15 μm.

[0086] The surface of the reflection electrode 24 may be a flat surface(i.e., a so-called “mirror-finished surface”) or a concave/convexsurface. If the reflection electrode 24 has a concave/convex surface,light incident on the reflection region R is reflected while beingdiffused, whereby it is possible to produce a white display of a colorthat is close to the paper white. For example, a portion of theinterlayer insulating film 18 (a portion that is located below thereflection electrode 24) can be formed to have a concave/convex surface,so that the reflection electrode 24 has a concave/convex surfaceconforming to the surface configuration of the interlayer insulatingfilm 18.

[0087] In the present embodiment, the height of the surface of the TFTsubstrate 100 a on the side of closer to the liquid crystal layer 50 inthe reflection region R is substantially equal to that in thetransmission region T.

[0088] The color filter substrate 100 b of the liquid crystal displaydevice 100 includes a transparent insulative substrate 40 (e.g., a glasssubstrate), and a color filter layer 42 is formed on one surface of thetransparent insulative substrate 40 that is closer to the liquid crystallayer 50. The color filter layer 42 is formed across both of thetransmission region T and the reflection region R. Typically, the colorfilter layer 42 includes red (R), green (G) and blue (B) color layers.

[0089] Transparent dielectric layers (hereinafter also referred tosimply as “transparent layers”) 44 a, 44 b and 44 c are provided inregions of the color filter layer 42 that correspond to reflectionregions R, i.e., regions opposing the reflection electrodes 24. Thetransparent layer 44 a is formed so as to oppose the reflectionelectrode 24 a overlapping with the storage capacitor line 13, thetransparent layer 44 b is formed so as to oppose the reflectionelectrode 24 b overlapping with the gate line 11, and the transparentlayer 44 c is formed so as to oppose the reflection electrode 24 coverlapping with the source line 12.

[0090] Typically, the transparent layers 44 a, 44 b and 44 c arecolorless and made of an acrylic resin, for example. In the presentembodiment, the transparent layers 44 a, 44 b and 44 c are all formedwith a thickness of 2.5 μm. The transparent layer 44 a opposing thereflection electrode 24 a is formed with a width of 35 μm as is thereflection electrode 24 a. Moreover, while the reflection electrodes 24b and 24 c are formed with a width of 4 μm, the transparent layers 44 band 44 c opposing the reflection electrodes 24 b and 24 c, respectively,are formed with a width of 15 μm so that they also oppose the reflectionelectrodes 24 b and 24 c of an adjacent picture element region. Notethat the width of the transparent layers 44 a, 44 b and 44 c hereinrefers to the width on the bottom surface thereof (the surface that isin contact with the color filter layer 42).

[0091] The counter electrode 46, which is made of a transparentconductive material such as ITO, for example, is formed so as to coverthe color filter layer 42 and the transparent layers 44 a, 44 b and 44c.

[0092] Furthermore, an alignment layer (not shown), which is made of apolymer material such as polyimide, for example, is formed on onesurface of each of the TFT substrate 100 a and the color filtersubstrate 100 b that is closer to the liquid crystal layer 50. Thealignment layers are subjected to a rubbing treatment. The TFT substrate100 a and the color filter substrate 100 b are attached to each othervia a sealant (e.g., an epoxy resin), and a liquid crystal material tobe the liquid crystal layer 50 is enclosed in the gap between thesubstrates.

[0093] In the present embodiment, the thickness of the liquid crystallayer 50 in the reflection region R is ½ of that in the transmissionregion T. Specifically, the thickness of the liquid crystal layer 50 is5.0 μm in the transmission region T, and 2.5 μm in the reflection regionR. The thickness Rd of the liquid crystal layer 50 in the reflectionregion R can be set to be ½ of the thickness Td of the liquid crystallayer 50 in the transmission region T by forming the transparent layers44 a, 44 b and 44 c so that the step height CFd of the color filtersubstrate 100 b is substantially equal to the thickness Rd of the liquidcrystal layer 50 in the reflection region R.

[0094] The liquid crystal display device 100 further includes a pair ofpolarizing plates (e.g., circular polarizing plates) 19 and 49 providedon the outer side of the pair of substrates, and an illuminator(backlight) 60 provided on one side of the device that is closer to theTFT substrate 100 a. The backlight 60 is made from any appropriatecombination of a light focusing film, a light guiding plate, areflection sheet, etc. It is preferred to use a backlight having a highlight efficiency.

[0095] In the liquid crystal display device 100 of the presentembodiment, the area ratio of the transmission region T in a pictureelement region is 65%, i.e., substantially the same value as those ofnormal transmission type liquid crystal display devices. The area ratioof the reflection region R in a picture element region is 16.5%. Sincethe liquid crystal display device 100 has the transmission region T andthe reflection region R in each picture element region, it is possiblenot only to display an image with a contrast as high as that of atransmission type liquid crystal display device when used indoor, butalso to display an image with a desirable visibility without the imagebeing faded even under very bright environments (e.g., in strong summersunshine).

[0096] Moreover, in the liquid crystal display device 100 of the presentembodiment, the transparent layers 44 a, 44 b and 44 c are formed on thecolor filter layer 42 in the reflection region R, whereby the height ofthe surface of the color filter substrate 100 b on the side of closer tothe liquid crystal layer 50 in the reflection region R is greater thanthat in the transmission region T, as illustrated in FIG. 2, forexample. Furthermore, the height of the surface of the TFT substrate 100a on the side of closer to the liquid crystal layer 50 in the reflectionregion R is substantially equal to that in the transmission region T.

[0097] Specifically, in the liquid crystal display device 100, a step isprovided only on the surface of the viewer-side substrate (the colorfilter substrate 100 b), thereby realizing a multi-gap structure. Inthis way, the proportion of the region that does not contribute to thedisplay (unused region) in a picture element region can be reduced so asto increase the proportion of the region that contributes to thedisplay, thereby improving the brightness. The reason therefor will nowbe described.

[0098]FIG. 3A and FIG. 3B schematically illustrate a conventional liquidcrystal display device 1000 in which a multi-gap structure is realizedby providing a step on the surface of an active matrix substrate 1000 a.FIG. 3A is a plan view schematically illustrating one picture element ofthe liquid crystal display device 1000, and FIG. 3B is a cross-sectionalview taken along line 3B-3B′ in FIG. 3A.

[0099] In the liquid crystal display device 1000, a reflection electrode1024 is formed on an interlayer insulating film 1018 formed on atransparent insulative substrate 1010, and a transparent electrode 1022is formed in an opening 1018 a in the interlayer insulating film 1018.The opening 1018 a, which is provided in the interlayer insulating film1018 so as to expose the transparent electrode 1022 therethrough, istapered, and the interlayer insulating film 1018 has a side surface 1018s that is inclined so as to surround the opening 1018 a. The reflectionelectrode 1024 is formed so as to cover the inclined side surface 1018s.

[0100] If the reflection electrode 1024 covering the inclined sidesurface 1018 s efficiently reflects ambient light to the viewer side,the region where the inclined side surface 1018 s is present functionsas the reflection region R. In practice, however, the average taperangle of the inclined side surface 1018 s is about 45°, whereby lightreflected by the reflection electrode 1024 on the inclined side surface1018 s undergoes repeated internal reflection, and substantially none ofsuch light is output from the color filter substrate to the viewer side.Thus, the region where the inclined side surface 1018 s is presentbecomes an unused region U that does not contribute to the display.

[0101] The present inventors have found that in atransmission/reflection combination type LCD of certain specifications,the proportion (area ratio) of the unused region U was 8% when the arearatio between the reflection region R and the transmission region T was72:28 and the area proportions of the reflection region R and thetransmission region T in a picture element region (i.e., the apertureratio) were 58.0% and 22.7%, respectively, for example.

[0102] The proportion of the unused region U increases as the proportionof the transmission region T in a picture element region increases. FIG.4 illustrates the relationship between the proportion of thetransmission region T in a picture element region (i.e., thetransmission aperture ratio) (%), and the area ratio (%) of the unusedregion U.

[0103] As illustrated in FIG. 4, the area ratio of the unused region Uis about 8% when the transmission aperture ratio is about 23%, whereasthe area ratio of the unused region U is about 25% when the transmissionaperture ratio is about 51%. Thus, the area ratio of the unused region Uincreases, thereby reducing the light efficiency, as the transmissionaperture ratio increases.

[0104] In contrast, in the liquid crystal display device 100 of thepresent embodiment, a multi-gap structure is realized by providing astep on the surface of the color filter substrate 100 b, whereby suchunused region as described above is not present. Thus, it is possible toimprove the light efficiency and to improve the brightness.

[0105] Note that in practice, the height of the surface of the TFTsubstrate 100 a in the reflection region R may be slightly differentfrom that in the transmission region T. For example, in a case where thereflection electrode 24 has a concave/convex surface, the average heightof the concave/convex surface of the reflection electrode 24 may beslightly higher than the height of the surface of the transparentelectrode 22. In the present specification, “the height of the surfacein the reflection region R being substantially equal to that in thetransmission region T” refers to the difference between the height ofthe surface in the transmission region T and that in the reflectionregion R being so small that substantially no unused region occurs(e.g., so that the interlayer insulating film has substantially notapered portion). Specifically, the height of the surface in thereflection region R can be said to be substantially equal to that in thetransmission region T when the difference therebetween is 0.3 μm orless. Note that in a case where the reflection electrode 24 has aconcave/convex surface, the difference between the average height of theconcave/convex surface and the height of the transparent electrode 22 ispreferably set to be 0.5 μm or less, so that the thickness of the liquidcrystal layer 50 can be easily controlled while making the height of thesurface of the picture element electrode 20 as uniform as possible.

[0106] As described above, the light efficiency can be improved byemploying the “first arrangement”, in which a step is provided on thesurface of the color filter substrate, without providing a step on thesurface of the active matrix substrate. The light efficiency can befurther improved by providing the reflection electrode 24 on an opaqueelement (e.g., the storage capacitor line 13) in each picture elementregion.

[0107]FIG. 5A, FIG. 5B and FIG. 6 schematically illustrate analternative liquid crystal display device 100′ according to Embodiment 1of the present invention.

[0108] The liquid crystal display device 100 includes the reflectionelectrodes 24 b and 24 c, which overlap with the gate line 11 and thesource line 12, respectively, and the transparent layers 44 b and 44 c,which oppose the reflection electrodes 24 b and 24 c, respectively. Incontrast, the liquid crystal display device 100′ includes no reflectionelectrode that overlaps with the gate line 11 or the source line 12, orno transparent layer that opposes the gate line 11 or the source line12. Thus, the liquid crystal display device 100′ is similar to theliquid crystal display device 100 except that the reflection electrodes24 b and 24 c and the transparent layers 44 b and 44 c are omitted.

[0109] In the liquid crystal display device 100′, the area ratio of thetransmission region T in a picture element region is 65%, and the arearatio of the reflection region R is 13.5%. In the liquid crystal displaydevice 100′, as compared with the liquid crystal display device 100, thearea ratio of the reflection region is smaller due to the reflectionelectrode 24 being partially omitted. Nevertheless, it is still possibleto display an image with a desirable visibility, as with the liquidcrystal display device 100.

[0110] Moreover, in the liquid crystal display device 100′, a step isprovided only on the surface of the viewer-side substrate (the colorfilter substrate 100 b), thereby realizing a multi-gap structure, as inthe liquid crystal display device 100. Thus, it is possible to increasethe proportion of the region in a picture element region thatcontributes to the display, thereby further improving the brightness.

[0111] Embodiment 2

[0112]FIG. 7 schematically illustrates a liquid crystal display device200 according to Embodiment 2 of the present invention. The liquidcrystal display device 200 is different from the liquid crystal displaydevice 100′ illustrated in FIG. 6 in that different materials are usedfor the color filter layer 42 in the reflection region R and the colorfilter layer 42 in the transmission region T.

[0113] A color filter layer 42 b formed in the transmission region T ismade of a material that has a relatively dark color (a material having awide color reproduction range) so that the color filter layer 42 b issuitable for displaying an image in the transmission mode. On the otherhand, a color filter layer 42 a formed in the reflection region R ismade of a material that has a relatively light color and a high opticaltransmittance so that the color filter layer 42 a is suitable fordisplaying an image in the reflection mode. In the present embodiment,the color filter layer 42 a in the reflection region R and the colorfilter layer 42 b in the transmission region T are formed with the samethickness.

[0114] The transparent dielectric layer (transparent layer) 44 a isformed on the color filter layer 42 a in the reflection region R.Herein, the width of the transparent layer 44 a is the same as that ofthe color filter layer 42 a, and the thickness of the transparent layer44 a is 2.5 μm. The thickness of the liquid crystal layer 50 is 5.0 μmin the transmission region T and 2.5 μm in the reflection region R.

[0115] In the liquid crystal display device 200 of the presentembodiment, the color filter layer 42 a in the reflection region R ismade of a material that is different from the material of the colorfilter layer 42 b in the transmission region T. In this way, the opticaldensity of the color filter layer 42 a in the reflection region R andthat of the color filter layer 42 b in the transmission region T can beset to values that are suitable for displaying an image in thereflection mode and in the transmission mode, respectively. Thus, it ispossible to realize a display with a high color purity and a highcontrast ratio in the transmission region T while realizing a bright andsharp display in the reflection region R.

[0116] Embodiment 3

[0117]FIG. 8 schematically illustrates a liquid crystal display device300 according to Embodiment 3 of the present invention. The liquidcrystal display device 300 is different from the liquid crystal displaydevice 200 illustrated in FIG. 7 in that the liquid crystal displaydevice 300 does not include a transparent dielectric layer on the colorfilter layer 42, with the thickness of the color filter layer 42 a inthe reflection region R being larger than the thickness of the colorfilter layer 42 b in the transmission region T, thereby providing a stepon the surface of the color filter substrate 100 b.

[0118] Herein, the color filter layer 42 b in the transmission region Tis formed with a thickness of 1 μm, and the color filter layer 42 a inthe reflection region R is formed with a thickness of 3.5 μm. Therefore,the height of the surface in the reflection region R is greater thanthat in the transmission region T by 2.5 μm, and the thickness of theliquid crystal layer 50 is 5.0 μm in the transmission region T and 2.5μm in the reflection region R.

[0119] In the liquid crystal display device 300 of the presentembodiment, the color filter layer 42 a in the reflection region R ismade of a material that is different from that of the color filter layer42 b in the transmission region T, whereby it is possible to realize adisplay with a high color purity and a high contrast ratio in thetransmission region T while realizing a bright and sharp display in thereflection region R, as with the liquid crystal display device 200.

[0120] Furthermore, in the liquid crystal display device 300 of thepresent embodiment, it is not necessary to form a transparent dielectriclayer on the color filter layer 42. Therefore, misalignment of atransparent dielectric layer does not occur, whereby it is possible tomore precisely produce the color filter substrate 100 b. Moreover, sincethe process of forming a transparent dielectric layer is omitted,thereby simplifying the production process. Furthermore, it is possibleto avoid a decrease in the transmittance or undesirable coloring due tothe provision of a transparent dielectric layer, thereby facilitatingthe design of the color filter layer 42 (the design of the color filtersubstrate 100 b).

[0121] Embodiment 4

[0122]FIG. 9A, FIG. 9B and FIG. 10 schematically illustrate a liquidcrystal display device 400 according to Embodiment 4 of the presentinvention. While the liquid crystal display devices 100, 200 and 300 ofEmbodiments 1, 2 and 3 employ the “first arrangement”, the liquidcrystal display device 400 of the present embodiment employs the “secondarrangement” in addition to the “first arrangement”.

[0123] The liquid crystal display device 400 of the present embodimentis different from the liquid crystal display device 100′ illustrated inFIG. 5A, FIG. 5B and FIG. 6 in that the color filter layer 42 includesan opening 42′ in a portion of the reflection region R.

[0124] As illustrated in FIG. 9B and FIG. 10, the color filter layer 42includes the opening 42′ formed in a portion of the reflection region R.A first transparent dielectric layer (hereinafter also referred tosimply as “first transparent layer”) 44 a 1 is formed in the opening42′. Furthermore, a second transparent dielectric layer (hereinafteralso referred to simply as “second transparent layer”) 44 a 2 is formedon a portion of the color filter layer 42 in the reflection region R andon the first transparent layer 44 a 1. The second transparent layer 44 a2 is formed with a thickness of 2.5 μm so as to oppose the reflectionelectrode 24 a, whereby the thickness of the liquid crystal layer 50 inthe reflection region R is one half (2.5 μm) of that in the transmissionregion T (5.0 μm).

[0125] In the present embodiment, the color filter layer 42 includes theopening 42′ formed in a portion of the reflection region R, and thefirst transparent layer 44 a 1 is formed in the opening 42′. Therefore,a portion of display light passing through the reflection region Rpasses through the first transparent layer 44 a 1, which is surroundedby the color filter layer 42. Therefore, in the reflection region R, animage is displayed by a mixture of light passing through the colorfilter layer 42 and light passing through the first transparent layer 44a 1 (the opening 42′). This improves the transmittance in the reflectionregion R, and the display in the reflection region R will not be dimmedeven if the thickness of the color filter layer 42 is set so as tooptimize the color purity in the transmission region T. As a result, itis possible to produce a bright display with a high color purity both inthe transmission region T and in the reflection region R.

[0126] The area of the opening 42′ of the color filter layer 42 (thearea thereof as viewed in the direction normal to the substrate) can beappropriately set according to the intended brightness or colorreproduction range. Conversely, the brightness and/or the colorreproduction range can be adjusted by changing the area of the opening42′. In a case where the size of a single picture element region is 80μm×240 μm, the size of the reflection region R is 60 μm×40 μm, and thethickness of the color filter layer 42 is 1 μm, the optical density inthe transmission region T can be substantially matched with the opticaldensity in the reflection region R (the optical density for reflectedlight that travels through the panel twice in the reflection region R)by setting the sizes of the opening 42′ of the color filter layer 42 tobe 25 μm×12 μm, for example.

[0127] Note that the area of the opening 42′ may be set to be the samefor different color layers (e.g., the same for all three colors of R, Gand B), or may alternatively be set to be different for different colorlayers depending on the intended brightness, color reproduction range;white point (chromaticity of white), etc., for the reflection region R.Moreover, the opening 42′ may be provided only for color layer(s) forwhich it is necessary.

[0128] An example of a method for forming the color filter layer 42, thefirst transparent layer 44 a 1 and the second transparent layer 44 a 2of the liquid crystal display device 400 of the present embodiment willbe described with reference to FIG. 11A to FIG. 11G. Note that themethod will be described below with respect to a case where the colorfilter layer 42 includes a red color layer 42R, a green color layer 42Gand a blue color layer 42B corresponding to R, G and B, respectively,and the step of forming a black matrix BM will also be described below.

[0129] First, a metal film (or a resin film) 41 is formed on thetransparent substrate 40, as illustrated in FIG. 11A, and then the metalfilm (or a resin film) 41 is patterned into a predetermined pattern,thereby forming the black matrix BM, as illustrated in FIG. 11B.

[0130] Then, a red photosensitive resin material is applied on thetransparent substrate 40 with the black matrix BM having been formedthereon, and is patterned into a predetermined pattern, thereby formingthe red color layer 42R, as illustrated in FIG. 11C. In this process,the patterning is performed so that the opening 42′ is formed in aportion of the region to be the reflection region R. Note that theapplication of the photosensitive resin material may be done by using aspin coat method or a dry film method, for example.

[0131] Similarly, the green color layer 42G is formed, as illustrated inFIG. 11D, by using a green photosensitive resin material, and then theblue color layer 42B is formed, as illustrated in FIG. 11E, by using ablue photosensitive resin material. In this way, the color filter layer42 including the red color layer 42R, the green color layer 42G and theblue color layer 42B is formed.

[0132] Then, a transparent dielectric material (e.g., a transparentresin material) is applied on the transparent substrate 40 with thecolor filter layer 42 having been formed thereon, and then the appliedtransparent dielectric material is patterned so as to leave each portionthat is located in the reflection region R, thereby forming the firsttransparent layer 44 a 1 and the second transparent layer 44 a 2, asillustrated in FIG. 11F. Then, the counter electrode 46 is formed byusing a transparent conductive material so as to cover the color filterlayer 42 and the second transparent layer 44 a 2, as illustrated in FIG.11G.

[0133] Note that while the method has been described above with respectto a case where the first transparent layer 44 a 1 and the secondtransparent layer 44 a 2 are formed integrally, they may alternativelybe formed separately. For example, after the steps of FIG. 11A to FIG.11E, the first transparent layer 44 a 1 is formed in the opening 42′ ofthe color filter layer 42, as illustrated in FIG. 12A, and then thesecond transparent layer 44 a 2 is formed on a portion of the colorfilter layer 42 in the reflection region R and on the first transparentlayer 44 a 1, as illustrated in FIG. 12B.

[0134] In a case where the first transparent layer 44 a 1 and the secondtransparent layer 44 a 2 are formed at once, undulations conforming tothe underlying surface configuration (i.e., the surface configuration ofthe color filter layer 42 including the openings 42′) may occur on thesurface of the second transparent layer 44 a 2, depending on the sizeand shape of the opening 42′, the type of the transparent dielectricmaterial, etc. Forming the first transparent layer 44 a 1 and the secondtransparent layer 44 a 2 separately, as illustrated in FIG. 12A and FIG.12B, is advantageous in that such undulations do not occur, whereby thethickness of the liquid crystal layer 50 in the reflection region R caneasily be made constant. On the other hand, forming the firsttransparent layer 44 a 1 and the second transparent layer 44 a 2 at onceintegrally, as illustrated in FIG. 11F, is advantageous in that theprocess can be simplified as compared with a case where they are formedseparately.

[0135] With an arrangement where the openings 42′ are provided in thecolor filter layer 42, as that in the present embodiment, the productionprocess can be simplified as compared with another arrangement wherecolor layers are formed by using different materials in the transmissionregion T and in the reflection region R, as those of the liquid crystaldisplay devices 200 and 300 of Embodiments 2 and 3. Moreover, with thearrangement of the present embodiment, it is not necessary to providetwo different materials for different color layers when forming thecolor filter layer 42, whereby it is possible to reduce the productioncost. Therefore, the arrangement is industrially very useful.

[0136] In a case where the color filter includes a red color layer, agreen color layer and a blue color layer, for example, the liquidcrystal display device 400 of the present embodiment can be obtained byperforming the step of forming a color layer of the color filter layer42 three times (once for each of R, G and B) before the formation offirst transparent layer 44 a 1 and the second transparent layer 44 a 2.In contrast, with the liquid crystal display device 200 of Embodiment 2,the step of forming a color layer of the color filter layer 42 needs tobe performed six times (twice for each of R, G and B) before theformation of the transparent layer 44 a. Also with the liquid crystaldisplay device 300 of Embodiment 3, the step of forming a color layer ofthe color filter layer 42 needs to be performed six times (twice foreach of R, G and B).

[0137] Since the liquid crystal display device 400 of the presentembodiment employs the “first arrangement”, in which a step is providedon the surface of the color filter substrate 100 b without providing astep on the surface of the TFT substrate 100 a, it is possible toimprove the light efficiency as with other liquid crystal displaydevices employing the “first arrangement” such as the liquid crystaldisplay devices 100, 200 and 300 of Embodiments 1, 2 and 3.

[0138] In addition, the liquid crystal display device 400 of the presentembodiment employs the “second arrangement”, i.e., the liquid crystaldisplay device 400 includes the first transparent layer 44 a 1 forcontrolling the optical density in the reflection region R by reducingthe existence proportion of the color filter layer 42 in the reflectionregion R from that in the transmission region T, and the secondtransparent layer 44 a 2 formed in the reflection region R so as to belocated closer to the liquid crystal layer 50 than the first transparentlayer 44 a 1 and the color filter layer 42 for controlling the height ofthe surface of the color filter substrate 100 b. Therefore, it ispossible to control the height of the surface of the color filtersubstrate 100 b in the reflection region R independently of the controlof the existence proportion of the color filter layer 42 in thereflection region R. Thus, it is possible to precisely and easilycontrol the optical density of the color filter layer 42 in thereflection region R and the thickness of the liquid crystal layer 50.

[0139] Embodiment 5

[0140]FIG. 13A, FIG. 13B and FIG. 14 schematically illustrate a liquidcrystal display device 500 according to Embodiment 5 of the presentinvention. The liquid crystal display device 500 of the presentembodiment is different from the liquid crystal display device 400 ofEmbodiment 4 in that the liquid crystal display device 500 includes aplurality of openings 42′ in each reflection region R. Moreover, theliquid crystal display device 500 is different from the liquid crystaldisplay device 400 also in that the storage capacitor line 13 and thereflection electrode 24 a are formed in a shape that is close to asquare shape.

[0141] In the liquid crystal display device 500 of the presentembodiment, the transmittance in the reflection region R is improved byforming the openings 42′ in the color filter layer 42, whereby it ispossible to simplify the production process and to reduce the productioncost, as with the liquid crystal display device 400 of Embodiment 4.

[0142] Moreover, in the liquid crystal display device 500, a pluralityof openings 42′ are formed in the color filter layer 42 in eachreflection region R, as illustrated in FIG. 13B and FIG. 14. As aresult, even if the first transparent layer 44 a 1 and the secondtransparent layer 44 a 2 are formed at once, undulations conforming tothe underlying surface configuration are unlikely to occur on thesurface of the second transparent layer 44 a 2. Therefore, the thicknessof the liquid crystal layer 50 in the reflection region R can easily becontrolled to be constant.

[0143] Furthermore, in the liquid crystal display device 500, thereflection electrode 24 a is formed in a shape that is close to a squareshape. As a result, in a case where the reflection electrode 24 a isformed with a concave/convex surface, the convex (concave) portions canbe arranged efficiently. Therefore, it is possible to improve thereflection characteristics of the reflection electrode 24 a.

[0144] Embodiment 6

[0145]FIG. 15 and FIG. 16 schematically illustrate liquid crystaldisplay devices 600A and 600B, respectively, according to Embodiment 6of the present invention. The liquid crystal display device 600Aillustrated in FIG. 15 is different from the liquid crystal displaydevice 200 of Embodiment 2 illustrated in FIG. 7 in that a transparentdielectric layer 44 a′ has a function of diffusing light. Moreover, theliquid crystal display device 600B illustrated in FIG. 16 is differentfrom the liquid crystal display device 500 of Embodiment 5 illustratedin FIG. 14 in that a first transparent dielectric layer 44 a 1′ and asecond transparent dielectric layer 44 a 2′ have a function of diffusinglight.

[0146] In the liquid crystal display device 600A, the transparent layer44 a′ has a function of diffusing (scattering) light. Herein, thetransparent layer 44 a′ is formed by using a material that contains anacrylic photosensitive transparent resin whose refractive index is 1.48mixed with 10% by volume of silica-based minute particles 48 whoserefractive index is 1.35. The haze value of the transparent layer 44 a′(a value that represents the light-diffusing property of the layer) is55%. Note that the refractive indices of the transparent resin and theminute particles 48, the amount of the minute particles 48 to be added,and the haze value of the transparent layer 44 a′, are not limited tothose values shown above, but can be appropriately set according to theintended display characteristics, etc.

[0147] In the liquid crystal display device 600A of the presentembodiment, light passing through the reflection region R is diffused(scattered) by the transparent layer 44 a′, whereby the lightreflectance in the reflection region R increases by 12% as compared withthat of the liquid crystal display device 200 of Embodiment 2. Moreover,this suppresses a rainbow-like coloring phenomenon due to thediffraction caused by the regularly arranged reflection electrodes 24 orthe concave/convex surface of the reflection electrodes 24, even under alight source that emits light having a high degree of collimation (e.g.,sunlight). Thus, the display quality is further improved.

[0148] Note that the effects of improving the reflectance andsuppressing the rainbow-like coloring phenomenon can be obtained byproviding the light-diffusing function by way of mixing alight-scattering material (minute particles made of silica or an acrylicresin) in an adhesive layer used for the adhesion between the polarizingplate 49 and the color filter substrate 100 b. In such a case, however,light passing through the transmission region T is also diffused,thereby reducing the contrast ratio and the transmittance. In contrast,in the liquid crystal display device 600A, the transparent layer 44 a′,which is selectively provided in the reflection region R has a functionof diffusing light, whereby it is possible to improve the displaycharacteristics in the reflection region R without affecting the displaycharacteristics in the transmission region T.

[0149] Note that while the transparent layer 44 a′ having the functionof diffusing light used herein is a layer that contains a matrixmaterial and particles whose refractive index is different from that ofthe matrix material, the present invention is of course not limitedthereto, but the transparent layer 44 a′ may alternatively be any otherappropriate layer that functions as a light-diffusing layer.

[0150] The first transparent layer 44 a 1′ and the second transparentlayer 44 a 2′ of the liquid crystal display device 600B illustrated inFIG. 16 have a function of diffusing light, as does the transparentlayer 44 a′ of the liquid crystal display device 600A. Herein, the firsttransparent layer 44 a 1′ and the second transparent layer 44 a 2′ aremade of the same material as the transparent layer 44 a′ of the liquidcrystal display device 600A.

[0151] In the liquid crystal display device 600B, the first transparentlayer 44 a 1′ and the second transparent layer 44 a 2′ have the functionof diffusing light, thereby obtaining effects as those of the liquidcrystal display device 600A.

[0152] Note that in liquid crystal display device 600B, both of thefirst transparent layer 44 a 1′ and the second transparent layer 44 a 2′have the function of diffusing light. Alternatively, only one of themmay have the function of diffusing light.

[0153]FIG. 17 schematically illustrates an alternative liquid crystaldisplay device 600C according to the present embodiment. The liquidcrystal display device 600C is similar to the liquid crystal displaydevice 400 illustrated in FIG. 10 except that the second transparentlayer 44 a 2′ has the function of diffusing light.

[0154] Also with the liquid crystal display device 600C, the effect ofimproving the display characteristics can be obtained, as with theliquid crystal display device 600A or the liquid crystal display device600B.

[0155] Note that in the present specification, the “transparentdielectric layer”, the “first transparent dielectric layer” and the“second transparent dielectric layer” may have the function of diffusinglight as described in the description of the present embodiment, and arenot required to be transparent in a strict sense. Specifically, theselayers are only required to be transparent to a degree such that lightcan be appropriately transmitted therethrough for displaying an image.

[0156] Embodiment 7

[0157]FIG. 18 schematically illustrates a liquid crystal display device700 according to Embodiment 7 of the present invention. The liquidcrystal display device 700 is different from the liquid crystal displaydevice 300 of Embodiment 3 illustrated in FIG. 8 in that a color filterlayer 42 a′ formed in the reflection region R has a function ofdiffusing light.

[0158] In the liquid crystal display device 700, the color filter layer42 a′ formed in the reflection region R has a function of diffusinglight. Herein, the color filter layer 42 a′ is formed by using amaterial that contains a color layer material whose refractive index is1.47 mixed with 10% by volume of the silica-based minute particles 48whose refractive index is 1.35. The haze value of the color filter layer42 a′ is 58%.

[0159] In the liquid crystal display device 700 of the presentembodiment, light passing through the reflection region R is diffused(scattered) by the color filter layer 42 a′ formed in the reflectionregion R, whereby the light reflectance in the reflection region Rincreases by 14% as compared with that of the liquid crystal displaydevice 300 of Embodiment 3. Moreover, it is possible to obtain adesirable display quality in which the rainbow-like coloring phenomenonis suppressed, as with the liquid crystal display devices 600A, 600B and600C of Embodiment 6. Moreover, since the color filter layer 42 a′selectively provided in the reflection region R has the function ofdiffusing light, it is possible to improve the display characteristicsin the reflection region R without affecting the display characteristicsin the transmission region T.

[0160] Embodiment 8

[0161] The structure of a liquid crystal display device 800 according toEmbodiment 8 of the present invention will now be described withreference to FIG. 19.

[0162] As illustrated in FIG. 19, the liquid crystal display device 800includes a rear substrate 800 a, a color filter substrate (frontsubstrate) 800 b opposing the rear substrate 800 a, and the liquidcrystal layer 50 provided therebetween.

[0163] As illustrated in FIG. 19, the transmission/reflectioncombination type LCD 800 includes the transmission region T and thereflection region R for each of a plurality of picture element regionsthat are arranged in a matrix pattern, and is capable of displaying animage in a transmission mode and in a reflection mode. An image can bedisplayed in either one of the transmission mode and the reflectionmode, or by using both display modes at the same time. The transmissionregion T is defined as a region of the rear substrate 800 a that has afunction as an electrode for applying a voltage across the liquidcrystal layer 50 and also a function of transmitting light therethrough.The reflection region R is defined as a region of the rear substrate 800a that has a function as an electrode for applying a voltage across theliquid crystal layer 50 and also a function of reflecting light.

[0164] The rear substrate 800 a includes the transparent insulativesubstrate (e.g., a glass substrate) 10, the insulating film 18 formed onthe transparent insulative substrate 10, and a column electrode 25having a stripe pattern and provided on the insulating film 18.

[0165] The column electrode 25 includes the transparent electrode 22formed on the insulating film 18, and the reflection electrode 24 formedon a portion of the transparent electrode 22. In the liquid crystaldisplay device 800, the reflection electrode 24 defines the reflectionregion R, and a portion of the transparent electrode 22 where thereflection electrode 24 is not formed defines the transmission region T.

[0166] The transparent electrode 22 is made of a transparent conductivematerial such as ITO, for example, and the reflection electrode 24 ismade of a high-reflectance metal such as aluminum, for example. In thepresent embodiment, the insulating film 18 has a concave/convex surfacebelow the reflection electrode 24, and the reflection electrode 24 has aconcave/convex surface conforming to the surface configuration of theinsulating film 18. Note that while the reflection electrode 24 is incontact with the transparent electrode 22 across the entire surfacethereof so as to be electrically connected to the transparent electrode22 in the present embodiment, the transparent electrode 22 and thereflection electrode 24 may alternatively be formed so that only aportion of the reflection electrode 24 is in contact with thetransparent electrode 22.

[0167] Furthermore, an alignment film 71 is formed so as to cover thecolumn electrode 25. The alignment film 71 used herein is of ahorizontal alignment type.

[0168] In the present embodiment, the height of the surface of the rearsubstrate 800 a on the side closer to the liquid crystal layer 50 in thereflection region R is substantially equal to that in the transmissionregion T. Note that in the present embodiment, the reflection electrode24 has a concave/convex surface and, strictly speaking, the averageheight of the concave/convex surface of the reflection electrode 24 maybe slightly greater than the height of the surface of the transparentelectrode 22. Note however that the difference between the height of thesurface in the transmission region T and that in the reflection region Ris so small that substantially no unused region occurs. Therefore, itcan be considered that the height of the surface in the reflectionregion R is substantially equal to that in the transmission region T.

[0169] The color filter substrate 800 b opposing the rear substrate 800a includes the transparent insulative substrate (e.g., a glasssubstrate) 40, as illustrated in FIG. 19. A first transparent dielectriclayer (first transparent layer) 47 a is formed on one surface of thetransparent insulative substrate 40 that is closer to the liquid crystallayer 50. The first transparent layer 47 a is formed in at least aportion of the reflection region R, and the color filter layer 42 isformed so as to cover the first transparent layer 47 a. In other words,the first transparent layer 47 a is formed in at least a portion of thereflection region R and is interposed between the transparent insulativesubstrate 40 and the color filter layer 42. Furthermore, a secondtransparent dielectric layer (second transparent layer) 47 b is formedon the color filter layer 42 in the reflection region R. Thus, thesecond transparent layer 47 b is located closer to the liquid crystallayer 50 than the first transparent layer 47 a and the color filterlayer 42.

[0170] In the present embodiment, the color filter layer 42 is formed sothat the thickness of the color filter layer 42 in at least a portion ofthe reflection region R is smaller than the thickness of the colorfilter layer 42 in the transmission region T. Specifically, thethickness of the color filter layer 42 on the first transparent layer 47a is smaller than that in other regions.

[0171] Moreover, the color filter substrate 800 b includes a rowelectrode 45 having a stripe pattern for applying a voltage across theliquid crystal layer 50. The row electrode 45 is formed so as to coverthe color filter layer 42 and the second transparent dielectric layer 47b. Furthermore, an alignment film 72 is formed so as to cover the rowelectrode 45. The alignment film 72 used herein is of a horizontalalignment type.

[0172] The liquid crystal layer 50 provided between the rear substrate800 a and the color filter substrate 800 b may be a liquid crystal layerof any of various modes known in the art. In the present embodiment, theliquid crystal layer 50 is an ECB (Electrically ControlledBirefringence) mode liquid crystal layer, and the incident light istransmitted/blocked in a controlled manner by using the birefringence ofthe liquid crystal layer 50. In the present embodiment, the thickness ofthe liquid crystal layer 50 in the reflection region R is smaller thanthat in the transmission region T. Specifically, the thickness of theliquid crystal layer 50 in the reflection region R is set to be ½ ofthat in the transmission region T. The height of the surface of the rearsubstrate 800 a on the side closer to the liquid crystal layer 50 in thetransmission region T is substantially equal to that in the reflectionregion R. Therefore, the thickness Rd of the liquid crystal layer 50 inthe reflection region R can be set to be ½ of the thickness Td of theliquid crystal layer 50 in the transmission region T by producing thecolor filter substrate 800 b so that the step height CFd of the colorfilter substrate 800 b is substantially equal to the thickness Rd of theliquid crystal layer 50 in the reflection region R.

[0173] A method for producing the liquid crystal display device 800 willnow be described. The production of the rear substrate 800 a of theliquid crystal display device 800 will not be described below because itcan be produced by using a method known in the art.

[0174] First, the color filter substrate 800 b is produced as follows.

[0175] First, the first transparent layer 47 a is formed on thetransparent insulative substrate 40 so as to be located in thereflection region R, as illustrated in FIG. 20A. Specifically, the firsttransparent layer 47 a is formed by a photolithography process using anacrylic photosensitive resin, for example. Of course, the firsttransparent layer 47 a may alternatively be formed by using othermethods such as a patterning method using etching, a printing method, ora transfer method.

[0176] Then, the color filter layer 42 is formed on the transparentinsulative substrate 40 with the first transparent layer 47 a havingbeen formed thereon, as illustrated in FIG. 20B. Specifically, eachcolor layer of the color filter layer 42 is formed by using an acrylicpigment-dispersed photosensitive resin, for example. As a photosensitiveresin to be a color layer is applied on the transparent insulativesubstrate 40, the surface, which has become a concave/convex surfacewith the first transparent layer 47 a thereon, is flattened to somedegree. As a result, the thickness of the color filter layer 42 (a colorlayer) on the first transparent layer 47 a is smaller than that in otherregions, as illustrated in FIG. 20B. Specifically, the thickness of thecolor filter layer 42 on the first transparent layer 47 a is reduced dueto the film thinning phenomenon.

[0177] Then, the second transparent dielectric layer 47 b is formed on aportion of the color filter layer 42 in the reflection region R, asillustrated in FIG. 20C. Specifically, the second transparent dielectriclayer 47 b is formed by a photolithography process using an acrylicphotosensitive resin, for example.

[0178] Then, the row electrode 45 is formed by using a transparentconductive material (e.g., ITO) on the color filter layer 42 and thesecond transparent dielectric layer 47 b, which have been formed asdescribed above, and the alignment film 72 is further formed thereon,thus obtaining the color filter substrate 800 b.

[0179] Then, the obtained color filter substrate 800 b and the rearsubstrate 800 a, which is provided separately, are attached to eachother with a predetermined gap therebetween. Note that before theattachment, one surface of each of the substrates that is to be closerto the liquid crystal layer 50 is subjected to an alignment treatment asnecessary. After the attachment of the color filter substrate 800 b andthe rear substrate 800 a, a liquid crystal material to be the liquidcrystal layer 50 is injected into the gap therebetween, thus obtainingthe liquid crystal display device 800.

[0180] As already described above, in a transmission/reflectioncombination type LCD, the number of times display light passes throughthe color filter layer in the transmission region is different from thatin the reflection region (i.e., once in the transmission region andtwice in the reflection region), whereby it is difficult to produce abright display with a high color purity both in the transmission regionand in the reflection region. If the optical density of the color filterlayer is set to be relatively high so as to optimize the color purity inthe transmission region, light passing through the reflection region isexcessively absorbed by the color filter layer, resulting in a darkdisplay in the reflection region. On the other hand, if the opticaldensity of the color filter layer is set to be relatively low so as toincrease the display brightness in the reflection region, the colorpurity in the transmission region decreases.

[0181] In the liquid crystal display devices 400 and 500 of Embodiments4 and 5, the opening 42′ is provided in a portion of the color filterlayer 42 in the reflection region R, as illustrated in FIG. 10, FIG. 14,etc., so as to suppress the decrease in the transmittance in thereflection region R, thereby realizing a bright display with a highcolor purity both in the transmission region T and in the reflectionregion R.

[0182] However, in a case where the opening 42′ is provided in the colorfilter layer 42, an image is displayed while light passing through thecolor filter layer 42 is mixed with light passing through the opening42′, not the color filter layer 42, in the reflection region R, wherebythe color purity (color reproduction range) may not be sufficiently highin the reflection region R.

[0183] In contrast, in the liquid crystal display device 800 of thepresent embodiment, the thickness of the color filter layer 42 in atleast a portion of the reflection region R is smaller than the thicknessof the color filter layer 42 in the transmission region T, therebysuppressing the decrease in the transmittance in the reflection regionR. Therefore, in the reflection region R, light that does not passthrough the color filter layer 42 does not need to be used fordisplaying an image, and it is possible to display an image by usingonly light that passes through the color filter layer 42. Thus, with theliquid crystal display device 800 of the present invention, a displaywith a sufficiently high color purity (color reproducibility) isrealized even in the reflection region R.

[0184] In the present embodiment, the first transparent layer 47 a isformed in at least a portion of the reflection region R so as to reducethe thickness of the color filter layer 42 on the first transparentlayer 47 a, thereby creating a thickness distribution as described abovein the color filter layer 42.

[0185] The thickness of the color filter layer 42 on the firsttransparent layer 47 a changes depending on the thickness, area, shape,etc., of the first transparent layer 47 a. Thus, by appropriatelysetting these parameters, it is possible to set the thickness of thecolor filter layer 42 on the first transparent layer 47 a to an intendedvalue, thereby obtaining an intended brightness and color reproductionrange.

[0186] In a case where the size of a single picture element region is 80μm×240 μm, the size of the reflection region R is 60 μm×40 μm, and thethickness of the color filter layer 42 is 1 μm, the optical density inthe transmission region T can be substantially matched with the opticaldensity in the reflection region R (the optical density for reflectedlight that travels through the panel twice in the reflection region R)by, for example, setting the size of the first transparent layer 47 a tobe 60 μm×40 μm, which is substantially the same as that of thereflection region R, and the thickness thereof to be 2 μm, therebysetting the thickness of the color filter layer 42 on the firsttransparent layer 47 a to be about 0.5 μm. Note that if the thickness Tdof the liquid crystal layer 50 in the transmission region T is 5 μm, thethickness of the second transparent layer 47 b can be set to be 1 μm,whereby the thickness Rd of the liquid crystal layer 50 in thereflection region R is 2.5 μm, i.e., ½ of the thickness Td of the liquidcrystal layer 50 in the transmission region T.

[0187] The present inventors have found that the relationship betweenthe shape and thickness of the first transparent layer 47 a and thethickness of the color filter layer 42 on the first transparent layer 47a generally has the following tendencies (1) to (3):

[0188] (1) As the thickness of the first transparent layer 47 aincreases, the thickness of the color filter layer 42 on the firsttransparent layer 47 a decreases.

[0189] (2) As the area proportion of the first transparent layer 47 a inthe reflection region R increases, the thickness of the color filterlayer 42 on the first transparent layer 47 a decreases.

[0190] (3) With the area proportion (total area) of the firsttransparent layer(s) 47 a in the reflection region R being fixed, thethickness of the color filter layer 42 on the first transparent layer 47a is smaller when a plurality of smaller first transparent layers 47 aare provided in each reflection region R than when a single firsttransparent layer 47 a is provided in each reflection region R. In otherwords, as the first transparent layers 47 a are formed in a discretemanner in the reflection region R, the thickness of the color filterlayer 42 on the first transparent layer 47 a is smaller. Moreover, withthe area proportion (total area) of the first transparent layer(s) 47 abeing fixed, the thickness of the color filter layer 42 on the firsttransparent layer 47 a is smaller as the number of the first transparentlayers 47 a is larger, i.e., as a larger number of smaller firsttransparent layers 47 a are formed in an island-like arrangement.

[0191] The thickness of the color filter layer 42 on the firsttransparent layer 47 a can be controlled by appropriately setting theshape and thickness of the first transparent layer 47 a in view of thetendencies (1) to (3) above.

[0192] As described above, the liquid crystal display device 800includes the first transparent dielectric layer 47 a for controlling theoptical density in the reflection region R by reducing the thickness ofthe color filter layer 42 in the reflection region R to be smaller thanthat in the transmission region T.

[0193] The liquid crystal display device 800 of the present embodimentfurther includes the second transparent dielectric layer 47 b formed inthe reflection region R so as to be located closer to the liquid crystallayer 50 than the first transparent dielectric layer 47 a and the colorfilter layer 42 for controlling the height of the surface of the colorfilter substrate 100 b. Therefore, it is possible to control the heightof the surface of the color filter substrate 100 b in the reflectionregion R independently of the control of the thickness of the colorfilter layer 42 in the reflection region R. Thus, it is possible toprecisely and easily control the optical density of the color filterlayer 42 in the reflection region R and the thickness of the liquidcrystal layer 50.

[0194] As the color filter layer 42 is formed so as to cover the firsttransparent layer 47 a, the surface of the color filter layer 42 isflattened by the film thinning phenomenon. However, the surface of thecolor filter layer 42 may not always be completely flat, but may be aconcave/convex surface as illustrated in FIG. 20B. Therefore, it is notimpossible to control the thickness of the liquid crystal layer 50 byusing the step height CFd, as in a liquid crystal display device 1100illustrated in FIG. 21, without providing the second transparent layer47 b.

[0195] In practice, however, it is difficult to simultaneously andoptimally control two values, i.e., the thickness of the color filterlayer 42 formed on the first transparent layer 47 a and the step heightof the color filter layer 42, only by controlling the thickness, shape,etc., of the first transparent layer 47 a.

[0196] For example, while the thickness of the color filter layer 42 onthe first transparent layer 47 a changes depending not only on thethickness and shape of the first transparent layer 47 a but also on thethickness of the color filter layer 42 in the transmission region T, thethickness of the color filter layer 42 in the transmission region T isautomatically determined by the color purity required in thetransmission region T and the optical density of the color layermaterial to be used. Under such restraint, it is difficult, only bycontrolling the thickness and shape of the first transparent layer 47 a,to set the thickness of the liquid crystal layer 50 in the reflectionregion R to be ½ of that in the transmission region T while controllingthe thickness of the color filter layer 42 on the first transparentlayer 47 a to be optimal for display in the reflection mode.

[0197] In contrast, the liquid crystal display device 800 of the presentembodiment includes the first transparent dielectric layer 47 a forcontrolling the optical density of the color filter layer 42 in thereflection region R and the second transparent dielectric layer 47 b forcontrolling the height of the surface of the color filter substrate 800b in the reflection region R, i.e., the liquid crystal display device800 employs the “second arrangement”. Therefore, it is possible toprecisely and easily control the optical density of the color filterlayer 42 in the reflection region R and the thickness of the liquidcrystal layer 50.

[0198] Note that in the present embodiment, a passive matrix type liquidcrystal display device has been described. Of course, effects as thoseof the present embodiment can be obtained, by employing a similararrangement, also with an active matrix type liquid crystal displaydevice including the TFT 30 as a switching element for each pictureelement region as in a liquid crystal display device 800′ illustrated inFIG. 22.

[0199] Embodiment 9

[0200] While liquid crystal display devices that employ the “firstarrangement” and the “second arrangement” have been described above inEmbodiments 4, 5, 6, 7 and 8, it is possible to precisely and easilycontrol the optical density of the color filter layer in the reflectionregion and the thickness of the liquid crystal layer even with a liquidcrystal display device that employs only the “second arrangement” butnot the “first arrangement”.

[0201]FIG. 23 schematically illustrates a liquid crystal display device900 according to Embodiment 9 of the present invention. The liquidcrystal display device 900 is different from the liquid crystal displaydevice 800′ of Embodiment 8 in that the liquid crystal display device900 does not employ the “first arrangement”.

[0202] In the liquid crystal display device 900, a step is provided onthe surface of a rear substrate 900 a. The height of the surface of therear substrate 900 a in the reflection region R is greater than that inthe transmission region T.

[0203] The thickness Rd of the liquid crystal layer 50 in the reflectionregion R can be set to be ½ of the thickness of the liquid crystal layer50 in the transmission region T by adjusting the thickness of the secondtransparent layer 47 b on a color filter substrate 900 b so that the sumof the step height Kd of the rear substrate 900 a and the step heightCFd of the color filter substrate 900 b is equal to the thickness Rd ofthe liquid crystal layer 50 in the reflection region R.

[0204] In a case where the size of a single picture element region is 80μm×240 μm, the size of the reflection region R is 60 μm×40 μm, thethickness Td of the liquid crystal layer 50 in the transmission region Tis 5 μm, the step height (the difference between the height in thereflection region R and that in the transmission region T) Kd of therear substrate 900 a is 1 nm, and the thickness of the color filterlayer 42 is 1 μm, the optical density in the transmission region T canbe made to be higher than the optical density in the reflection region R(the optical density for reflected light that travels through the paneltwice in the reflection region) by for example, setting the size of thefirst transparent dielectric layer 47 a to be 60 μm×40 μm, which issubstantially the same as that of the reflection region R, and thethickness thereof to be 1 μm, thereby setting the thickness of the colorfilter layer 42 on the first transparent dielectric layer 47 a to beabout 0.7 μm. Then, the thickness of the second transparent dielectriclayer 47 b can be set to be 0.8 μm, whereby the step height CFd of thecolor filter substrate 900 b is 1.5 μm and the thickness of the liquidcrystal layer 50 in the reflection region R is 2.5 μm, i.e., ½ of thethickness of the liquid crystal layer 50 in the transmission region T.

[0205]FIG. 24 schematically illustrates an alternative liquid crystaldisplay device 900′ according to Embodiment 9 of the present invention.The liquid crystal display device 900′ is different from the liquidcrystal display device 900 in that the opening 42′ is formed in thecolor filter layer 42, thereby suppressing the decrease in thetransmittance in the reflection region R. Nevertheless, the liquidcrystal display device 900′ includes a first transparent dielectriclayer 41 a for controlling the optical density of the color filter layer42 in the reflection region R and a second transparent dielectric layer41 b for controlling the thickness of the liquid crystal layer 50,whereby it is possible to precisely and easily control the opticaldensity of the color filter layer 42 in the reflection region R and thethickness of the liquid crystal layer 50, as with the liquid crystaldisplay device 900.

[0206] While the present invention has been described in preferredembodiments, it will be apparent to those skilled in the art that thedisclosed invention may be modified in numerous ways and may assume manyembodiments other than those specifically set out and described above.Accordingly, it is intended by the appended claims to cover allmodifications of the invention that fall within the true spirit andscope of the invention.

1-23. (Canceled)
 24. A liquid crystal display device, comprising: anactive matrix substrate: a color filter substrate including atransparent substrate and a color filter layer located closer to theactive matrix substrate than the transparent substrate; a liquid crystallayer provided between the active matrix substrate and the color filtersubstrate; and a picture element region including a transmission regionin which an image is displayed in a transmission mode, and a reflectionregion in which an image is displayed in a reflection mode, wherein: athickness of the liquid crystal layer is less in the reflection regionthan in the transmission region; a height of a surface of the colorfilter substrate on a side closer to the liquid crystal layer in thereflection region is greater than that in the transmission region; andthe color filter substrate includes a first transparent dielectric layerformed on the transparent substrate and covered or surrounded by thecolor filter layer, and a second transparent dielectric layer providedin the reflection region so as to be located closer to the liquidcrystal layer than the first transparent dielectric layer and the colorfilter layer.
 25. The liquid crystal display device of claim 24 whereina height of a surface of the active matrix substrate on a side closer tothe liquid crystal layer in the reflection region is substantially equalto that in the transmission region.
 26. The liquid crystal displaydevice of claim 24, wherein the first transparent dielectric layer isformed between the transparent substrate and the color filter layer andis covered by the color filter layer.
 27. The liquid crystal displaydevice of claim 26 wherein the color filter layer in the reflectionregion is made of a material that is different from that of the colorfilter layer in the transmission region.
 28. The liquid crystal displaydevice of claim 24, wherein the color filter layer includes at least oneopening in a portion of the reflection region and the first transparentdielectric layer is formed in the at least one opening and is surroundedby the color filter layer.
 29. A liquid crystal display device,comprising: an active matrix substrate, a color filter substrateincluding a transparent substrate and a color filter layer locatedcloser to the active matrix substrate than the transparent substrate; aliquid crystal layer provided between the active matrix substrate andthe color filter substrate; and a picture element region including atransmission region in which an image is displayed in a transmissionmode, and a reflection region in which an image is displayed in areflection mode, wherein: a thickness of the liquid crystal layer isless in the reflection region than in the transmission region; a heightof a surface of the color filter substrate on a side closer to theliquid crystal layer in the reflection region is greater than that inthe transmission region: and the color filter layer in the reflectionregion is made of a material that is different from that of the colorfilter layer in the transmission region.
 30. The liquid crystal displaydevice of claim 24, wherein a transparent dielectric layer provided inthe reflection region so as to be located closer to the liquid crystallayer than the color filter layer.
 31. The liquid crystal display deviceof claim 30, wherein a height of a surface of the active matrixsubstrate on a side closer to the liquid crystal layer in the reflectionregion is substantially equal to that in the transmission region.
 32. Aliquid crystal display device, comprising: an active matrix substrate; acolor filter substrate including a transparent substrate and a colorfilter layer located closer to the active matrix substrate than thetransparent substrate; a liquid crystal layer provided between theactive matrix substrate and the color filter substrate: and a pictureelement region including a transmission region in which an image isdisplayed in a transmission mode, and a reflection region in which animage is displayed in a reflection mode, wherein: a thickness of theliquid crystal layer is less in the reflection region than in thetransmission region; a height of a surface of the color filter substrateon a side closer to the liquid crystal layer in the reflection region isgreater than that in the transmission region; the color filter layerincludes at least one opening in a portion of the reflection region; andthe first transparent dielectric layer is formed in the at least oneopening and is surrounded by the color filter layer.
 33. The liquidcrystal display device of claim 32, wherein a height of a surface of theactive matrix substrate on a side closer to the liquid crystal layer inthe reflection region is substantially equal to that in the transmissionregion.